(Renal Calculi, Nephrolithiais)
Kidney stones are pieces of a stone or crystal-like material that form inside the kidneys or urinary tract. The kidneys are two bean-shaped organs located in the lower back. Their main function is to remove waste from the body and to balance the water and electrolyte content of the blood by filtering the salt and water in the blood. The waste and water excreted by the kidneys combine to form urine.
There are several types of kidney stones. The most common type contains mostly calcium along with phosphate or oxalate. Others contain uric acid, struvite, and/or cystine.
Approximately 50% of kidney stones are due to unknown causes. Some of the known causes include:
- Chemotherapy for cancer (ie, uric acid stone)
- Too much oxalate in urine (hyperoxaluria)
- Too little magnesium in urine (hypomagnesiuria)
- Too much calcium in the urine (hypercalciuria)
- Too much calcium in the blood (hypercalcemia)
- Too little citrate in the urine (hypocitraturia)
- Tiny bacteria around which a stone can form
- To much uric acid in the urine (hyperuricuria, gout)
- Bacteria that produce enzymes that increase the amount of ammonia and therefore struvite in the urine (this allows struvite stones to form)
- An inherited abnormality in the way the body handles cystine
A risk factor is something that increases your chance of getting a disease or condition. Risk factors for kidney stones include:
- Race: white
- Sex: male
- Age: 20-50 years old
- Geographical location (residents of the Southeast United States have an increased risk)
- Family members who have had kidney stones or gout
- Previous kidney stones
- Taking calcium supplements or vitamin D in excessive doses
- Low birth weight babies receiving intravenous feedings
- Other medical conditions, including:
- High blood pressure
- Kidney disease
- Overactive parathyroid
- Chronic diarrhea
- Ulcerative colitis
- Crohn's disease
- Urinary tract infections
- Immobility, paralysis, being bedridden
- Medications, including:
- Several drugs used in the treatment of AIDS
- Cancer chemotherapy agents
- Previous intestinal bypass surgery
- Reduced fluid intake or increased fluid loss in hot weather
Occasionally kidney stones do not cause symptoms and they leave the body in the urine. Kidney stones often, however, cause severe pain.
- Sharp, stabbing pain in the lower back that may occur every few minutes lasting from 20 minutes to one hour
- Pain in the lower abdomen and groin area, labia, or testicles
- Nausea, vomiting, or diarrhea
- Blood in the urine
- Frequent urge to urinate
- Burning pain during urination
The doctor will ask about your symptoms and medical history, and perform a physical exam.
Tests may include:
Urinalysis–to look for blood, pus, bacteria, and crystals in the urine
Blood Tests–to check kidney function, calcium, and uric acid levels
Urine Culture–if infection suspected
Spiral CT Scan–a type of x-ray that uses a computer to make pictures of the inside of the kidney
Ultrasound–a test that uses sound waves to examine the kidneys
Intravenous Pyelogram (IVP)–special x-ray that produces images of the urinary system (less commonly used today)
24 Hour Urine–to check levels of calcium, phosphorus, uric acid, oxalate, and citrate
Treatment depends on the size and location of the kidney stone. Treatment may include the following:
For small kidney stones, drinking at least two or three quarts of water a day helps the body pass the stone in the urine. The doctor may provide a special cup or strainer to catch the stone when it passes so that it can be analyzed. If you are having a hard time keeping fluids down, you may need to be hospitalized to receive intravenous fluids.
Medications and Nerve Stimulation
You can take pain medication (ketorolac, a NSAID, or even narcotic analgesics) as needed. In addition, you may need intravenous or intramuscular pain medication.
There is also recent evidence that medications commonly used to treat high blood pressure–calcium channel blockers and alpha blockers–may facilitate the passage of kidney stones.
New research suggests that transcutaneous electrical nerve stimulation (TENS), which applies low-voltage electrical current to electrodes pasted on the skin (to the side of the abdomen and back in this case) might also be effective in relieving pain
Surgery for stone removal may be necessary if it is:
- Very large or growing larger
- Causing continued bleeding or damage to the kidney
- Causing infection
- Blocking the flow of urine
Types of surgery include:
Ureteroscopy and Stone Basketing–a scope is slipped up the urethra, into the bladder, and into the ureter. A tiny basket is used to try to snare the stone.
Stent Placement–if the ureter is obstructed, a tiny tube may be placed in the ureter to allow urine to pass, and to try to avoid kidney damage.
Extracorporeal Shock Wave Lithotripsy (ESWL)–this procedure uses shock waves to break up stones that are too large to pass. It requires anesthesia and may cause blood in the urine and minor back pain for a few days.
Percutaneous Nephrolithotomy–uses a scope placed through an incision in the side of the abdomen to remove a kidney stone that is too big to pass.
Lithotomy–open surgery to remove a kidney stone. This surgery is rarely used now.
Once you have formed a kidney stone, you are more likely to form another. Here are some steps to prevent more stones from forming:
- Drink plenty of fluids, especially water.
- Don't change your diet without consulting your doctor. Recommendations will be based on the type of stones you've had, and the results of your 24-hour urine tests. Be sure to ask your doctor for a list of the foods you should avoid, or meet with a dietitian who can help you understand your dietary restrictions. You may be advised to do the following:
- Avoid apple and grapefruit juices.
- Increase intake of cranberry juice.
- Avoid foods high in oxalate, such as spinach.
- If tests show your urine is unusually acidic, you may need to eat less meat, fish, and poultry. These foods increase urine acidity.
- If you have calcium stones, you may be asked to decrease your sodium intake.
- Increase your intake of magnesium.
- Increase your fiber intake.
- If you have an enlarged parathyroid gland, you may need to have it removed surgically.
- Medications may include:
- Drugs that control the amount of acid in the urine
- Allopurinol or sodium cellulose phosphate to treat urine high in calcium
- Hydrochlorothiazide (a diuretic)
- Thiola to reduce the amount of cystine in the urine